1. Field of the Invention
This invention relates to a power unit having an internal combustion engine and a transmission. More particularly, the present invention concerns the lubricating system and the relationship of the lubricating system between the internal combustion engine and the transmission.
2. Description of the Relevant Art
An engine is an assembly that derives power by converting combustion energy, obtained by combusting fuel, into mechanical energy. In the case of a reciprocating engine, the engine includes a crankshaft, a primary reduction output gear provided on the crankshaft, and a crankcase covering the crankshaft and the primary reduction output gear.
A hydrostatic infinitely variable transmission is an assembly where a fixed capacity swash plate-type hydraulic pump and a variable capacity hydraulic motor are located on the same axis, so that an infinitely variable transmission output can be obtained by varying the swash plate of the hydraulic motor on the output side. A hydrostatic infinitely variable transmission is well known, and examples are given in Japanese Patent Publication Hei. 8-26929 and Japanese Patent No. 2696520.
According to the background art, a case member defines a dedicated engine crank chamber and a dedicated transmission chamber. Separate dedicated oil is used as oil for driving and engine oil for engine lubrication. In other words, a vehicle having a hydrostatic infinitely variable transmissions has an engine section and a hydrostatic infinitely variable transmission section defined as separate chambers, each having separate oil supplies.
The background art suffers drawbacks. The volume or size of the power unit, which includes the internal combustion engine and the hydrostatic infinitely variable transmission is relatively large and bulky. Further, the engine oil and the hydrostatic infinitely variable transmission oil have to be managed separately by an owner or service person, and replication of parts occurs in operating the two systems separately.
The present invention has as an object to provide an internal combustion engine power unit which resolves one or more of the drawbacks associated with the background art.
In accordance with the present invention a hydrostatic infinitely variable transmission is built-into the engine crankcase. By integrally building the hydro-static infinitely variable transmission into the engine crankcase, a dedicated chamber for housing the hydro-static infinitely variable transmission can be elimated, and the internal combustion engine power unit can be made more compact, and oil can also be used in common.
Other objects and further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.